Not Applicable
Not Applicable
(1) Field of the Invention
The field of the invention is pressurized cans suitable for the transport and discharge of reactive products for the production of foams and for surface techniques.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
The invention concerns a pressurized can with a can body, a valve positioned in a dome, a bottom with inset crimp disc and an inner shell with a pry-off closure positioned on the crimp disc, a ram with a section inside of and a section outside of the inner shell and a sealing element, which is in particular suitable for the transport and discharge of reactive products for the production of foams and for surface techniques.
The invention primarily relates to the design of pressurized cans that contain, aside from the main component fluid substances that are required for the creation and discharge of polyurethane or similar foams, a second component in the inner shell which reacts with the main component to form the final product, the actual insulating foam. However, the invention can be used equally well for 2-component formulations for other purposes, for instance in surface techniques, for example, for multi-component finishes.
As a rule, the substances contained in the pressurized container are liquid and consist of a prepolymer, a foaming agent, if necessary, and the fluid propellant gas that is used to discharge the components. The additional component is present in a relatively small amount and mostly consists of a compound that reacts quickly with the main component, for example, for polyurethane prepolymers with reactive isocyanate groups, a cross-linking agent in the form of, for instance, a hydroxyl compound and catalysts, if necessary. The component in the inner shell is used to influence, as a rule to accelerate, the hardening and quality of the foam. As a rule, the second component is introduced into the pressurized can shortly before discharge of the foam by prying off the inner container cover, and is mixed there by shaking.
A pressurized can with a single-piece bottom formed from a metal forming piece is known from DE-U-82 27 229.8. The neck of the additional container, which has an outside thread, is introduced into a recess in this bottom, and secured from the outside by screwing on a nut and compressing an O-ring seal between the shoulder of the additional container and the inner rim of the bottom recess. The sealed rod, which, in its turn, is executed as a piston-shaped seal in the interior of the additional container, is designed as an arbor that turns in and rests against the inside of the neck of the additional container. If the arbor is driven from the outside, this leads to positive contact between its inner end and the cover of the additional container, causing it to be pried off into the can against the internal pressure.
The invention itself is based on WO-A-85 00 157, which describes a pressurized can for discharging single or multi-component substances that contains an additional container in its interior for holding an additional component. The inner container has an inner cover that can be pried off by a rod that passes through the bottom of the pressurized can into the interior of the inner container. The ram is movably mounted inside the additional container and passes through a seal located in the crimp disc of the can bottom. A pressurized can according to EP-A-0 148 211 is shown in FIG. 1.
Both pressurized cans according to current techniques require relatively expensive design and assembly. In addition, the container according to DE-U-82 27 229 suffers from a relatively complicated mechanism. Although the cover is pried off against the relatively large internal pressure of the container by the rotary movement of the rod, this requires a relatively large amount of effort and, in addition, requires a complex and expensive seal system.
Although the pressurized can according to WO-A-85 00 157 has proven itself overall and represents a significant improvement compared to the mentioned registered design, introducing the ram through the rubber seal mounted in the crimp disc is problematic and requires a non-optimal ram geometry.
The invention is therefore based on the problem of further developing the pressurized can according to WO-A-85 00 157 so that the parts of the inner shell are more easily assembled to form a non-separating and perfectly sealed unit and so that at the same time a user needs to exert relatively little force to cause the closure part of the inner shell to be pried off.
This problem is solved by the pressurized can of the type initially mentioned, in that the inner shell is injection molded onto the crimp disc, the inner shell has a shaft for the ram that projects through the center of the crimp disc and ends underneath the crimp disc, the ram has a sealing element that acts against and is movable within the shaft and the ram has an inner and an outer limiting element that limit the path length of the ram.
It is essential for the pressurized can according to the invention that the inner shell of the pressurized can is injection molded onto the crimp disc. This measure creates an integral connection between the inner shell and the crimp disc that results in the inner shell being fixed immovably above the bottom of the pressurized can, in an expedient manner, the crimp disc has holes in the part of its bottom into which injection molding is performed, through which the injection molding compound can penetrate and reinforce the connection between crimp disc and inner shell.
The inner shell has a shaft that passes through the open center of the crimp disc and ends above the crimp disc. At the same time, the ram has a sealing element that acts against the inner shaft wall and is movable within the shaft and which seals the interior of the inner shell at the bottom. The seal to the can interior is provided by a closure element located at the upper end of the shaft, a cover for instance. The sealing element, which is movable inside the shaft, also serves to guide the ram in the interior of the inner shell.
In order to set limits on the free path length of the ram in the axial direction, the ram has an inner and an outer limiting element, the inner limiting element located above or on the dome side of the sealing element and the other below or on the bottom side of the sealing element. On the one hand, the limiting elements prevent the ram from being pulled too far out of the inner shell and, on the other, prevent it from being pushed in too far when the closure is pried off. In both cases, the sealing element would lose its contact with the shaft and, is consequently, its ability to provide a seal.
In the part of the crimp disc around which injection molding has been performed, there is preferably a section extending axially that is undercut when viewed from the outside and engages inside the outer wall of the inner shell. In a preferred embodiment, an O-ring is present in this undercut, which, on the one hand, exerts a certain inward pressure on the crimp disc and, on the other, serves as an additional seal between inner shell and crimp disc. The O-ring works against the pressure of the propellant present in the pressurized can, which acts in particular in the bottom region and can produce deformations there, and prevents infiltration of the shell.
The sealing element on the ram is likewise expediently an O-ring positioned in a groove encircling the ram. The seal, together with the ram, can be moved along the inner wall of the shaft and allows the ram to move inwards a prescribed path length in order to pry off the shell closure, with path length determined by the outer limiting element.
The shaft expediently has a smooth even rim on its inner or dome-side end that serves as a seat for the inner or dome-side limiting element on the ram. The inner limiting element is preferably a disc or a disc-shaped projection. If this disc is at the rim of the shaft, the ram is at the lower or outer end or resting position, i.e. in the position in which the can is secured and can be stored and transported.
The outer limiting element is located on the ram below the sealing element, i.e. on the side of the ram towards the bottom. It acts in combination with a corresponding abutment on the inner wall of the shaft that defines an upper end position for the limiting element and therefore determines how tar the ram can be pushed into the shaft or inner shell. The room for movement of the ram between the end-stop points of the inner and outer limiting elements corresponds to the path that the ram must travel in order to move from its resting position and ensure that the inner shell closure is pried off. The abutment consequently defines the upper or inner end position of the ram following activation of the inner shell.
The outer limiting element is preferably a projection in the form of a truncated cone circling the ram that widens in the direction of the inner shell or the dome of the can. The abutment acting in combination with the limiting element consists preferably of two opposing projections from the inner wall of the shaft that are approximately circular segment-shaped.
In order to conserve volume, the ram itself has a cross-shaped cross-section. In order to ensure that it acts optimally in combination with the above-described abutment for the outer limiting element, the ram cross-section is unequal in the vicinity of the outer abutment, i.e. with short arms opposite to one another and long arms opposite to one another. The shorter arms make a more extreme elastic deformation of the truncated cone possible in their vicinity, so that during assembly the ram can be pushed through the inner shell into the shaft and the outer limiting element can be moved past its abutment. The truncated cone consequently acts as a stop only in the direction of the can interior.
In an preferred embodiment, the ram has a head on its dome-side end that has a diameter that essentially corresponds to the inside diameter of the inner shell. xe2x80x9cEssentiallyxe2x80x9d means here that the diameter is slightly smaller than the inside diameter of the inner shell, so that, on the one hand, a guideway is guaranteed and, on the other, sufficient play is available so that the ram can be guided effortlessly, if necessary past flat projections used to fix the closure in place, and can therefore fulfil its purpose. So that the head does not take up too much volume, it is expediently multi-vaned, having in particular a cross-shaped cross-section. In this regard, it has proven to be advantageous if the head is beveled in its vane region, i.e. the tip of one vane defines the point of the ram that is farthest from the bottom and the remaining parts of the head fall back smoothly. In this way, point contact is made with the inner shell closure in the vicinity of the shell wall so that the force exerted by the ram can be transferred optimally.
The inner shell expediently has a cover put onto it, which is sealed to the inner shell by an O-ring. In order to achieve a positive connection, it is furthermore expedient to provide a point-form or circumferential projection on the inner wall of the inner shell that engages in a corresponding groove in the cover.
A special and independent aspect of this invention is the design of the inner shell closure for pressurized cans as an extension of the inner shell, which, in turn, again has the above-described cover. This extension of the inner shell can, as described above for the cover, be put onto the inner shell and is sealed against the pressurized can contents by an O-ring. This variant allows inner shells for a variety of volumes to be prepared that can be opened with a uniform pry-off mechanism. This allows the volume of the inner shell to be easily adjusted to the can size and the intended use.
The Inner shell preferably has, in particular when a head with multiple vanes is present, a guide extending longitudinally that is useful when inserting the ram into the shaft. The guide allows the ram to be positioned in such a way that the collar in the vicinity of the short arms of the ram, as described above, passes by the point-form abutments of the shaft with which it acts in combination.
The invention concerns, in accordance with another independent feature, a cap that acts in combination with the outer ram end via a central receptor. For this purpose, the ram expediently has a cylindrical knob that is positively received by a corresponding cylindrical receptor in the cap. This measure leads to the ram knob having a defined position within the cap and allows the mixing process to be easily activated.
The cap itself has a cylinder-shaped wall that can engage into the space formed by the axially extending side boundaries of the crimp disc.
In accordance with a special embodiment, the cap has a ring on the wall that is mounted so that it can move axially and that acts in combination with an external wall projection via an inner circumferential projection and defines a lower or outer end position of the cap. The ring acts as an adapter shell and a connection between the can bottom or crimp disc and the cap.
In accordance with another preferred embodiment, the ring itself has an outer circumferential bead that engages inside, behind an axial side wall of the crimp disc, i.e. is mounted in the crimp disc itself. In this way, the cap is held on the can bottom and is, at the same time, movably mounted in such a way that the ram knob that it holds can be pushed into the can interior to activate the inner shell by pushing the cap. Naturally, the free path of the ram defined by the length of the adapter shell must be matched to the path defined by the outer limiting element, i.e. must essentially agree with it. Since the pressurized can contents are under pressure, activation of the inner shell must not lead to failure of the seal between inner shell and can bottom allowing the can contents a free path through this opening.
In order to define an upper or inner end position of the cap, i.e. the nearest possible position of the cap relative to the can bottom, it is advantageous for the cover of the cap to protrude on the sides and form an end stop for the ring or adapter shell.